Induction of heme oxygenase-1 (HSP32) mRNA in skeletal muscle following contractions.

The capacity of preexisting antioxidant pathways to handle oxidative stress during exercise may be complemented by the synthesis of inducible heat stress proteins (HSP). Our purpose was to determine if the amount of mRNA for HSP32, a major oxidative stress protein, was increased in muscle after repetitive contractions. Reverse transcriptase-polymerase chain reaction analysis showed that HSP32 mRNA (normalized to alpha-actin mRNA) was increased about seven- and about fourfold (P < 0.35) immediately after 1 h of exhaustive running and after 3 h of muscle contractions (10 Hz nerve stimulation), respectively. Northern blot analysis revealed that HSP70 mRNAs were 3.5- to 15.5-fold above control value (P < 0.05), whereas the content of another oxidative stress protein mRNA (macrophage stress protein 23) was unchanged 0 h after contractions. The relative increase in HSP32 mRNA was found to be dependent on active tension generation; passive tension did not increase the HSP32-to-actin mRNA ratio. Increases in HSP32 mRNA may underlie an inducible antioxidant pathway in muscle responsive to metabolic stresses associated with repeated muscle contractions.